After reading articles like this recent one in NYT, I was left with the impression that Twitter's "Promoted Tweets" ads are triggered when people search for advertisers by their name. See this quote, for example:

"When people are searching on Starbucks, what we really want to show them is that something is happening at Starbucks right now, and Promoted Tweets will give us a chance to do that," said Chris Bruzzo, vice president of brand, content and online at Starbucks.

It turns out that the ads, much like Google AdWords, can be triggered by a bunch of other search terms, including product names or even third-party brands. I noticed that BestBuy's ads are live too (Starbucks's ads went on air earlier this week) and spent some time plugging different terms into the search box to see what will come up.

I am still trying to understand the logic that guides the display of the ads. It seems that there is a list against which the search terms are checked. The search term (or a variation) needs to be present in the tweet itself, although not every word in a tweet will make it a "promoted" tweet. The list with the terms must be updated pretty often for the recently published tweets to show up as ads; either that, or the tweets must be scheduled in advance.

Searches for tri-color or Chickenfoot (a BestBuy concert) -- words that can be found in this and this tweets, respectively -- produced nothing.

Some trademarked terms trigger BestBuy's ads as well. Search for iPad, and this tweet about iPad arrival comes up. Search for Nook, and you get a Nook tweet-ad. Search for Bosch, though, and this tweet about Bosch appliances (published before the ad platform announcement) does not come up.

MediaPost yesterday wrote that this ad model could open a "PPC trademark can of worms."